Preservation of perishable goods, food in particular, typically involves preventing the growth of bacteria, fungi (such as yeasts), and other micro-organisms, as well as retarding the oxidation of fats that cause rancidity. Food preservation can also involve inhibiting enzymatic processes, which lead to discoloration and/or changes in texture of the perishable goods. In addition to or concurrent with visual deterioration, maintaining nutritional value and flavor is also an important aspect of food preservation.
There are a number of techniques that have been traditionally used to enhance preservation of perishable items. These include, for example, drying, pasteurization, refrigeration, freezing, vacuum packing, salting or curing, sugaring, smoking, chemical additives, pickling, lye, canning and bottling, irradiation, etc.
More recently, food coating (sometimes referred to as glazing) has been exploited as a means of enhancing preservation, as well as organoleptic properties. Several classes of biopolymers have been contemplated as coating materials: polysaccharides, proteins, lipids, as well as various combinations of these biopolymers (reviewed, for, example, in: Biopolymers—New Materials for Sustainable Films and Coatings. Copyright © 2011 John Wiley & Sons, Ltd., Editor(s): David Plackett; Print ISBN: 9780470683415; Online ISBN: 9781119994312; CH. 10 “Food Packaging Applications of Biopolymer-Based Films”; CH. 11 “Biopolymers for Edible Films and Coatings in Food Applications”; contents of which are incorporated herein by reference). Polysaccharides and proteins are known to form films with good mechanical properties, but with poor permeability, while the lipids form brittle films but with improved permeability. Coating fruits and vegetables with a waxing material is also a common example. The primary reasons for waxing are to prevent water loss and thus retard shrinkage and spoilage, and to improve appearance. The waxing materials used for such purposes depend to some extent on regulations in the country of production and/or export; both natural waxes (e.g., sugar-cane, carnauba, shellac, and resin) and petroleum-based waxes are used. Wax may be applied in a volatile petroleum-based solvent but is now more commonly applied via a water-based emulsion. Blended paraffin waxes applied as an oil or paste are often used on vegetables. Such techniques are useful for selective products, but not for others.